Laser welding methods that involve irradiating laser beam onto a T-shaped joint between a flange material and a web material, have been studied as methods for producing shaped steel such as T-shaped steel or H-shaped steel, which is used for instance in beams that make up building frames of buildings.
As illustrated in Patent literature 1, for instance, two metal plates are butted perpendicularly to each other, and two laser beams are irradiated simultaneously, along the butting section, onto opposing positions, from both the front and rear faces of the butting metal plates.
In such a method, laser beam is irradiated onto the butting section from the directions of both sides of the web material, which is not necessarily efficient in terms of enhancing productivity.
Therefore, the applicants proposed a method that involves irradiating laser onto the butting section only from the direction of one face of the web material. See, for instance, Patent literature 2.
To produce a building member in which a T-shaped welded joint is formed by pressing of edge section of a second metal plate perpendicularly to a first metal plate, this method involves relying on laser welding through irradiation of laser beam, as the welding method, with laser beam being irradiated at an inclination angle of 30 degrees or less with respect to the first metal plate, in such a manner that the second metal plate melts, over the entire thickness thereof, at the end section at which the second metal plate is pressed.
Patent literature 1: Japanese Patent Application Publication No. 2005-21912
Patent literature 2: Japanese Patent Application Publication No. 2007-307591